Inventor API 2025 Getactive object is not getting!

[pranav_sRUHFs]

System.Runtime.InteropServices.Marshal.GetActiveObject cannot be found usually!   am getting this exception while running my code on inventor 2025 version.  below is my code sample. am getting document

Dim _invApp As Inventor.Application

Public Sub New()

' This call is required by the designer.
InitializeComponent()

Try
_invApp = Marshal.GetActiveObject("Inventor.Application")
Catch ex As Exception
Try
Dim invAppType As Type =
GetTypeFromProgID("Inventor.Application")

_invApp = CreateInstance(invAppType)
_invApp.Visible = True
Catch ex2 As Exception
MsgBox(ex2.ToString())
MsgBox("Unable to get or start Inventor")
End Try
End Try
' Add any initialization after the InitializeComponent() call.

End Sub.

same code is running for 2024 inventor version.

1. reference dll is added exact dll for inventor 2025 version
2. i tried to build the same code in .net 8 i can't add winforms.
3. i tried to upgrade the code as per inventor user manual Port .Net Framework-based project to .Net    https://help.autodesk.com/view/INVNTOR/2025/ENU/?guid=GUID-522FF5BC-7CC5-43D5-99B1-14840CF54A82 

This porting also does not loaded my dll 

4.no mistakes in my addin manifest also. cause its loads for 2025 also as a button 

can someone help?

[WCrihfield]

Hi @pranav_sRUHFs.

System.Runtime.InteropServices.Marshal.GetActiveObject method is defined for .NET Framework only.

Microsoft.Visualbasic.Interaction.GetObject method is both .NET Framework and regular .NET.

I have been using the second one (GetObject) in my iLogic rules for several years now, but I am still using 2024.3 right now.

[Michael.Navara]

See this post for solution.

[JelteDeJong]

In my blog post "Migration addins to .Net core 8 (Inventor 2025)" I have a solution for this problem. See the part "Create Class Marshal2" (Almost at the bottom of the post.)